This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Phytochromes comprise a principal family of red/far-red light sensors in plants. We will attempt structure determination of the GAF domain of a phototaxis regulator phytochrome (PixJ), comprising the domain which houses the chromophore - phycocyanobilin (or PVB?). The constructs photoconvert and is only ~20 kDa;we would like to also determine its Pb andf Pg forms upon blue/green light exposure.